Method and apparatus for transmitting a RACH preamble on a wireless network

ABSTRACT

A first configuration of a first set of random access channel occasions can be received in a handover command message from a first cell. A second configuration of a second set of random access channel occasions of a second cell can be received. System information of the second cell can include the second configuration of the second set of random access channel occasions. A random access channel preamble can be transmitted on a random access channel occasion. The first set of random access channel occasions and/or the second set of random access channel occasions can include the random access channel occasion.

BACKGROUND 1. Field

The present disclosure is directed to a method and apparatus fortransmitting a RACH preamble on a wireless network.

2. Introduction

Presently, wireless communication devices, such as user equipment,communicate with other communication devices using wireless signals.When a Network Entity (NE), such as a Base Station (BS) or gNodeB (gNB),can create a number of narrow beams using a large number of antennaelements, the NE may transmit more than one Synchronization Signal (SS)block per period. Each SS block carries Primary and SecondarySynchronization Signals (PSS/SSS) and a Physical Broadcast Channel(PBCH) which may be Transmit (Tx) beamformed. A SS burst set includingone or more SS blocks, such as up to 64 SS blocks, may cover differentintended spatial directions.

With potentially transmitting multiple SS blocks according to apredefined pattern for SS block locations, the NE may need to provide aUser Equipment (UE) with SS block timing information, such as an indexof a given SS block of the SS burst set, and/or SS burst set timinginformation, such as an index of the SS burst set. After detecting atleast one SS block associated with NE Tx beams for the UE, the UE candetermine full or partial timing information, by using at least theknowledge on the predefined potential SS block locations, such as SSblock locations assumed by the UE, and the received SS block timinginformation. The full or partial information can include symbol timing,such as a symbol boundary, can include slot timing, such as a slotboundary, and can include frame timing, such as a frame boundary.

For mobility measurement and reporting, the UE may perform mobilitymeasurement for one or more SS blocks in the SS burst set based onsignals in each SS block, such as SSS and/or Demodulation ReferenceSignal (DMRS) of the PBCH. Further, a measurement report may includemeasurement quantities, such as Reference Signal Received Power (RSRP),of detected and measured one or more SS blocks and corresponding SSblock indices.

In Long Term Evolution (LTE), a RACH configuration index, such as Table5.7.1-2/3/4 in 3GPP TS 36.211, determines the RACH preamble format andthe time and frequency resources for the RACH preamble. In fifthgeneration (5G) new RAT, support of dynamic Time Division Duplex (TDD)operation and potential Ultra-Reliable Low-Latency Communication (URLLC)services make it difficult to predefine an uplink slot or the number ofuplink symbols in a slot. Accordingly, semi-static configuration of RACHtime and frequency resources may not be sufficient for flexible radioresource utilization.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of thedisclosure can be obtained, a description of the disclosure is renderedby reference to specific embodiments thereof which are illustrated inthe appended drawings. These drawings depict only example embodiments ofthe disclosure and are not therefore to be considered to be limiting ofits scope. The drawings may have been simplified for clarity and are notnecessarily drawn to scale.

FIG. 1 is an example block diagram of a system according to a possibleembodiment;

FIG. 2 is an example illustration of SS Timing Information Block (STIB)and Master Information Block (MIB) RE mapping on PBCH according to apossible embodiment;

FIG. 3 is an example, illustration of joint encoding of STIB and MIBaccording to a possible embodiment;

FIG. 4 is an example illustration of PBCH mapping within the PBCH TTIwhere the SS burst set periodicity is set to 20 ms and the PBCH TTI isset to 80 ms according to a possible embodiment;

FIG. 5 is an example illustration of SSS mapping within 20 ms default SSburst set periodicity where the SS burst set periodicity is set to 5 msaccording to a possible embodiment;

FIG. 6 is an example flowchart illustrating the operation of a wirelesscommunication device according to a possible embodiment;

FIG. 7 is an example flowchart illustrating the operation of a wirelesscommunication device according to a possible embodiment;

FIG. 8 is an example flowchart illustrating the operation of a wirelesscommunication device according to a possible embodiment;

FIG. 9 is an example flowchart illustrating the operation of a wirelesscommunication device according to a possible embodiment; and

FIG. 10 is an example block diagram of an apparatus according to apossible embodiment.

DETAILED DESCRIPTION

Some embodiments can provide a method and apparatus for communicating ona wireless network. According to a possible embodiment, a SS of a SSblock of a SS burst set can be received. A measurement can be performedat least on the received SS of the SS block. A PBCH of the SS block canbe received. The PBCH can include a first portion of the PBCH and asecond portion of the PBCH. The first portion of the PBCH can carry atleast a part of minimum system information. The second portion of thePBCH can carry timing information. The timing information can includeinformation including at least an indication of a SS block index of theSS block within the SS burst set. The second portion of the PBCH can bedemodulated and decoded. The SS block index of the SS block within theSS burst set can be determined at least based on the demodulating anddecoding. A measurement report can be transmitted. The measurementreport can include a measurement quantity from the measurement on thereceived SS of the SS block and can include the determined SS blockindex.

According to another possible embodiment, an indication of a set ofsemi-statically configured RACH resources can be received via a higherlayer signaling. The higher layer can be higher than a physical layer.An indication of availability of a RACH resource of at least one RACHresource of the set of semi-statically configured RACH resources can bereceived via a dynamic physical-layer signaling. The dynamicphysical-layer signaling can be within a number of slots including aRACH slot. The RACH slot can include the at least one RACH resource ofthe set of semi-statically configured RACH resources. An available RACHresource in the RACH slot can be determined based on the receivedindication of the set of semi-statically configured RACH resources andbased on the received indication of availability of the RACH resource ofthe at least one RACH resource of the set of semi-statically configuredRACH resources. A RACH preamble can be transmitted on the available RACHresource in the RACH slot.

FIG. 1 is an example block diagram of a system 100 according to apossible embodiment. The system 100 can include a User Equipment (UE)110, at least one network entity 120 and 125, such as a base station,and a network 130. The UE 110 can be a wireless wide area networkdevice, a user device, wireless terminal, a portable wirelesscommunication device, a smailphone, a cellular telephone, a flip phone,a personal digital assistant, a personal computer, a selective callreceiver, an Internet of Things (IoT) device, a tablet computer, alaptop computer, or any other user device that is capable of sending andreceiving communication signals on a wireless network. The at least onenetwork entity 120 and 125 can be wireless wide area network basestations, can be NodeBs, can be enhanced NodeBs (eNBs), can be New Radio(NR) NodeBs (gNBs), such as 5G NodeBs, can be unlicensed network basestations, can be access points, can be base station controllers, can benetwork controllers, can be Transmission/Reception Points (TRPs), can bedifferent types of base stations from each other, and/or can be anyother network entities that can provide wireless access between a UE anda network.

The network 130 can include any type of network that is capable ofsending and receiving wireless communication signals. For example, thenetwork 130 can include a wireless communication network, a cellulartelephone network, a Time Division Multiple Access (TDMA)-based network,a Code Division Multiple Access (CDMA)-based network, an OrthogonalFrequency Division Multiple Access (OFDMA)-based network, a Long TermEvolution (LTE) network, a NR network, a 3rd Generation PartnershipProject (3GPP)-based network, a satellite communications network, a highaltitude platform network, the Internet, and/or other communicationsnetworks.

In operation, the UE 110 can communicate with the network 130 via atleast one network entity 120. For example, the UE can send and receivecontrol signals on a control channel and user data signals on a datachannel.

Methods can be used to transmit a PBCH with supporting both wideband andnarrowband UEs. Two different SS block transmission modes can be useddepending on a cell operating mode and/or deployment scenarios andrelated configuration signaling. Embodiments can provide an efficientway to deliver the SS timing information in a PBCH to a UE withoutrequiring full decoding of the PBCH.

Embodiments can further provide SS timing indication and RACH resourceconfiguration. Some embodiments can provide for transmitting SS timinginformation, such as a SS block index and/or a SS burst set index, in aPBCH that does not mandate a UE to decode a neighbor cell's MasterInformation Block (MIB) before handover and supports combining multiplePBCHs within a PBCH Transmit Time Interval (TTI) to achieve reliablePBCH decoding. Some embodiments can provide for accommodating adaptationof SS burst set periodicities, such as 5, 10, 20, 40, 80, and 160 ms,with a fixed PBCH TTI. Some embodiments can provide for flexiblydetermining RACH time and frequency resources with support of dynamicTDD operation.

If SS block timing information bits, such as a SS block index within aSS burst set, are encoded together with other minimum System Information(SI) bits carried by PBCH, the information bits for PBCH may bedifferent for every SS block within the SS burst set. Furthermore, ifmore than one SS burst set can be transmitted per PBCH TTI and if theirtiming information, such as a SS burst set index within PBCH TTI, isalso explicitly indicated and encoded together with the other SI inPBCH, then the number of Broadcast Channel (BCH) Transport Blocks (TBs),at least differing in the timing information, per PBCH TTI can be verylarge. For example, the number of BCH TBs can be up to the maximumnumber of SS blocks within the SS burst set multiplied by the maximumnumber of SS burst sets per PBCH TTI. This may significantly increasePBCH encoding complexity at a Network Entity (NE), such as a gNodeB, andmay negatively impact network power consumption. In addition, it may bedifficult or not feasible for a UE to combine multiple PBCHs within agiven SS burst set and across SS burst sets within the PBCH TTI forreliable PBCH decoding. Thus, the PBCH resource may have to beoverprovisioned to achieve a certain target coverage, which potentiallyleads to a larger PBCH resource overhead. Furthermore, a UE in a RadioResource Control (RRC) connected mode may have to perform full PBCHdecoding for every detected neighbor cell, in order to reportmeasurement quantities together with corresponding SS block indices.Mandating the RRC connected UE to decode the entire PBCH from a neighborcell to perform mobility measurement and report can result in a longermeasurement gap or delay due to UE's full decoding of the PBCH. Inaddition, decoding PBCH for every detected cell can increase UE powerconsumption.

Implicit indication of the SS block timing information, such as use ofdifferent PBCH redundancy versions, can allow a UE to combine multiplePBCHs within the SS burst set. Accordingly, a UE can improve PBCHdemodulation performance. However, the method of implicit indication maystill require full PBCH decoding to obtain SS timing information.

FIG. 2 is an example illustration 200 of SS Timing Information Block(STIB) and MIB RE mapping on PBCH according to a possible embodiment. APBCH can carry two information blocks, such as a STIB and a MIB. Also,each information block can be separately encoded, modulated to aseparate set of Quadrature Amplitude Modulation (QAM), such asQuadrature Phase Shift Keying (QPSK), symbols, and mapped to a differentset of Resource Elements (REs) in the PBCH. The set of REs assigned forthe MIB in the PBCH can be denoted as M-PBCH REs, and another set of REsassigned for the STIB can be denoted as S-PBCH REs, where M-PBCH cancarry MIB and S-PBCH can carry STIB. The M-PBCH REs and S-PBCH REs canbe mutually exclusive. Resource partition between M-PBCH and S-PBCH inthe PBCH can be dependent on the sizes of MIB and STIB and required coderates of S-PBCH and M-PBCH in each SS block, taking into accountdifferent combining levels for M-PBCH and S-PBCH. For example, a S-PBCHcarrying 6-bit STIB can occupy 144 REs over 72 Subcarriers (SCs), andM-PBCH carrying 50-bit MIB can occupy 432 REs over 288 SCs minus the SCsfor the STIB, as shown in the illustration 200. The S-PBCH REs and/orM-PBCH REs can be mapped on to one or more OFDM symbols, such as 2 OFDMsymbols. In one example, the S-PBCH REs can be mapped on one symbolfollowing the SSS while M-PBCH REs can be mapped to multiple OFDMsymbols. In another example, the S-PBCH REs can be mapped only to REswithin the frequency band/region corresponding to the PSS/SSS. AssumingQPSK modulation, the example RE allocation can result in a code rate of0.021 for S-PBCH and a code rate of 0.058 for M-PBCH, in one SS block.With combining of 3 or more M-PBCHs, a UE can achieve similar decodingperformances for M-PBCH and S-PBCH. Additionally, the number of REsallocated for S-PBCH can be determined such that STIB decodingperformance in a given SS block can be similar to or better than aone-shot detection rate of PSS/SSS. Alternatively, M-PBCH REs canpartially or fully overlap with S-PBCH REs, and a UE can first decodeS-PBCH and cancel the S-PBCH interference to decode M-PBCH.

FIG. 3 is an example, illustration 300 of joint encoding of STIB and MIBaccording to a possible embodiment. The STIB and MIB can be jointlyencoded, but the resulting channel bits can be separated into twoself-decodable units, where a UE can decode the STIB from a first unitand can decode the MIB from a second unit. The first unit can include atleast the STIB as systematic bits and can include a fractional part ofthe MIB and parity bits that are generated by using the STIB and thefractional part of the MIB. In one example, the parity bits included inthe first unit can be a portion of the jointly coded parity bits thatare primarily based on the STIB systematic bits and an optionalfractional part of the MIB. For example, the parity bits can havesignificant contribution from the STIB systematic bits and optionalfractional part of the MIB included in first unit. The second unit caninclude at least the MIB as systematic bits and may include a full orpart of the STIB and parity bits resulting from the MIB and the full orpart of the STIB. In another example, the second unit can include atleast the remaining portion of the jointly coded bits that have not beenincluded in the first unit, such as at least the portion of the MIBsystematic bits, and at least the portion of the jointly coded paritybits not included in the first unit. The first and second units can bemodulated to different sets of modulation symbols and mapped todifferent sets of REs in the PBCH. The illustration 300 shows jointencoding of STIB and MIB. S-PBCH can represent the set of REscorresponding to first unit, and M-PBCH can represent the set of REscorresponding to second unit.

According to another possible embodiment, the STIB and MIB can bejointly encoded resulting in encoder output of a systematic bit stream,such as STIB and MIB, and a parity bit stream. At least the systematicbits corresponding to the STIB and a first portion of the parity bitsfrom the parity bit stream can be QAM, such as QPSK, modulated andmapped to a first set of REs, such as S-PBCH REs, of the PBCH REs. Thefirst portion of the parity bits can correspond to parity bits that havea significant contribution from at least the STIB systematic bits. Theremaining portion of the systematic bit stream and parity bit stream notincluded in the first set of REs can be QAM, such as QPSK, modulated andmapped to the remaining REs of the PBCH, such as M-PBCH REs. Thisremaining portion may or may not be self-decodable. In one example, atleast the systematic bits corresponding to the MIB and a second portionof the parity bits from the parity bit stream can be QAM, such as QPSK,modulated and mapped to the remaining REs of the PBCH. The secondportion of the parity bits can correspond to the parity bits of theparity bit stream not included in the first portion of the parity bits.

According to a possible embodiment, at least the STIB bits can be mappedto a portion of the joint encoder input information bit stream that haveequal or higher reliability relative to the other information bits inthe information bit stream. For, example, the joint encoder can be apolar code and the STIB bits can be mapped to virtual channels of thepolar code that have equal or lower error probability compared to theremaining virtual channels of the polar code.

According to a possible embodiment, the STIB and MIB can have separateCyclic Redundancy Check (CRC) parity bits. In another possibleembodiment, joint CRC parity bits can be computed from both the STIB andMIB bits. In another possible embodiment, CRC can only be based on MIBbits.

Separate encoding of SS timing information from a MIB or joint encodingof the SS timing information and the MIB, such as generation of twoself-decodable units carrying different systematic bits from jointdecoding, can allow a UE to not perform full decoding of PBCH forneighbor cell measurement and reporting. Furthermore, a UE can combinemultiple M-PBCHs for MIB decoding, which can increase reliability of MIBdecoding.

The MIB can include at least a part of a System Frame Number (SFN) andcan include other minimum system information. The minimum systeminformation can refer to essential system information that UE may needto acquire to access to a cell or a network. The MIB size including CRCbits can be smaller than 100 bits. According to a possible embodiment,the SFN can be a number between 0 and 1023 indicating an index of a 10ms radio frame. The STIB can include at least a SS block index and canfurther include a part of SFN and/or a SS burst set index. The size,such as the number of bits, of the STIB can be determined by the maximumnumber of SS blocks within a SS burst set and by the maximum number ofSS burst sets whose indices are explicitly indicated by the STIB. Forexample, if the MIB carries the 7 Most Significant Bits (MSBs) out of10-bit SFN, the PBCH TTI is 80 ms, the maximum number of SS blocks perSS burst set is 64, and the minimum SS burst set periodicity is 5 ms,then the STIB can carry at least 6 bits for the SS block index and canbe up to 10 bits, such as 6 bits for the SS block index and 4 bits forthe SS burst set index within the PBCH TTI.

Alternative embodiments can be used for information elements of theSTIB. One embodiment for information elements of the STIB can use a SSblock index, such as 6 bits, within a SS burst set to support up to 64SS blocks. A UE can combine multiple S-PBCHs across SS burst sets.According to a possible implementation, a SS burst set index within aPBCH TTI assuming the smallest SS burst set periodicity can be includedin the MIB and can be jointly encoded with the other SI in the MIB. Thiscan allow a UE to combine multiple M-PBCHs within a SS burst set, butthe UE may not combine M-PBCHs across multiple SS burst sets. In someexamples, the UE may be able to combine a portion of the M-PBCHs acrossmultiple SS burst sets, such as depending on how the joint encoding isperformed.

According to another possible implementation, a SS burst set indexwithin the PBCH TTI, assuming the default SS burst set periodicity, canbe included in the MIB and jointly encoded with the other SI in the MIB.This can allow a UE to combine multiple M-PBCHs across multiple SS burstsets within the default SS burst set periodicity, if the SS burst setperiodicity is configured to be smaller than the default SS burst setperiodicity. A SS burst set index within the default SS burst setperiodicity can be implicitly indicated. In one example, differentscrambling sequences can be applied to M-PBCHs for different SS burstsets within the default SS burst set periodicity. In another example,PSS or SSS sequences can be used to indicate the SS burst set indexwithin the default SS burst set periodicity. In another example, one ormore of different scrambling sequences applied to M-PBCHs, redundancyversion of M-PBCH, PSS, SSS sequences, or combination thereof can beused to indicate the different SS burst sets within the default SS burstset periodicity. The scrambling sequence may be generated from ascrambling code generator such as a gold code generator. The scramblingcode generator may be (re)initialized every default SS burst setperiodicity or PBCH TTI. In one example, there may be only one SS burstset with the default SS burst set periodicity. In various examples, thesame scrambling sequence may be used for all M-PBCH within a SS burstset. In some examples, the same redundancy version of M-PBCH may be usedfor all M-PBCH within a SS burst set.

FIG. 4 is an example illustration 400 of PBCH mapping within the PBCHTTI where the SS burst set periodicity is set to 20 ms and the PBCH TTIis set to 80 ms according to a possible implementation. FIG. 5 is anexample illustration 500 of SSS mapping within 20 ms default SS burstset periodicity where the SS burst set periodicity is set to 5 msaccording to a possible implementation. A SS burst set index within aPBCH TTI may not be included in the MIB but can be indicated implicitly.In one example, different scrambling sequences and/or a differentredundancy version can be applied to M-PBCHs per the default SS burstset periodicity within the PBCH TTI as shown in the illustration 400.The PSS or SSS sequences can be used to indicate the SS burst set indexwithin the default SS burst set periodicity as shown in the illustration500. A UE can combine multiple M-PBCHs across multiple SS burst setswithin the PBCH TTI. In various examples, the same scrambling sequencemay be used for all M-PBCH within a default SS burst set periodicity. Insome examples, the same redundancy version of M-PBCH may be used for allM-PBCH within a default SS burst set periodicity.

Another embodiment for information elements of the STIB can use a SSblock index within a SS burst set, such as 6 bits, and use a SS burstset index within a PBCH TTI assuming the default SS burst setperiodicity, such as 2 bits for the case of 80 ms PBCH TTI and thedefault SS burst set periodicity of 20 ms. A UE can combine multipleS-PBCHs across SS burst sets within the default SS burst setperiodicity.

Another embodiment for information elements of the STIB can use a SSblock index within a SS burst set, such as 6 bits, and use a SS burstset index within a PBCH TTI assuming the smallest SS burst setperiodicity, such as 4 bits for the case of 80 ms PBCH TTI and thesmallest SS burst set periodicity of 5 ms. A UE can combine multipleS-PBCHs across the PBCH TTIs.

Another embodiment for information elements of the STIB can use a SSblock index within a SS burst set, such as 6 bits, and use a radio frameindex within a PBCH TTI, such as 3 bits for the case of 80 ms PBCH TTI.With 5 ms SS burst set periodicity, the SSS can indicate frame timingboundary. A UE can combine multiple S-PBCHs across SS burst sets withina radio frame.

According to another possible embodiment, modulated symbols for STIB canbe mapped to a sub-band overlapping in the frequency domain with thesub-band where PSS/SSS are transmitted. Then, a UE can operate with thebandwidth the same as the PSS/SSS bandwidth for inter-frequency neighborcell measurement. If the bandwidth of the PBCH is larger than thePSS/SSS bandwidth, the above described mapping of S-PBCH symbols in thefrequency domain can allow UE to operate with the smaller bandwidth thanthe PBCH bandwidth for neighbor cell measurement. This can reduce UEpower consumption.

In the example illustration 200 described above, a PBCH bandwidth cancorrespond to a bandwidth of 288 consecutive subcarriers and the PBCHcan span 2 OFDM symbols within a SS block, while the bandwidth for thePSS and the SSS can correspond to a bandwidth of 144 consecutivesubcarriers. Similar to PSS/SSS, the PBCH can be transmitted withpredefined subcarrier spacing and a predefined transmission bandwidth.The S-PBCH can be mapped to the center 72 subcarriers of the 2 OFDMsymbols of the PBCH resource.

According to another possible embodiment, a UE receiver can combinechannel bits for STIB only across SS burst sets, and the gNodeB cantransmit the STIB with low code rate by allocating overprovisionedresource elements for S-PBCH. According to an alternative possibleembodiment, a part of the STIB can be encoded, such as 4 MSBs out of 6bits, and information corresponding to the remaining Least SignificantBits (LSB) can be implicitly indicated with scrambling sequences appliedto channel bits of S-PBCH. Then, a UE can combine a couple of S-PBCHsfrom consecutive SS blocks within the SS burst set and can potentiallyexploit beam diversity.

According to a possible embodiment, the MIB can have 50 bits includingCRC bits. The DL bandwidth for 2 bits can be 25, 50, 75, or 100 ResourceBlocks (RBs). The number of RBs can be a function of the carrierfrequency band and the 2 bits may map to a different set of RBs for adifferent frequency band. For example, 100, 200, 300, or 400 RBs can beused for 28-40 GHz frequency band. The MIB can include a part of systemframe number information, such as 7 bits. The MIB can includeinformation regarding remaining minimum SI transmission, such as 10bits. The MIB can include configuration information for a PhysicalDownlink Control Channel (PDCCH) scheduling a Physical Downlink SharedChannel (PDSCH) carrying the remaining minimum SI. The configurationinformation can include a frequency distance from a SS raster, such as acenter frequency of PSS/SSS, to a starting subcarrier of a CommonControl Channel Resource Set (CORESET), which can be used for schedulinga common PDSCH. The configuration information can include the size ofthe common CORESET in terms of the number of symbols and the number ofResource Block Groups (RBGs). The configuration information can includethe location, such as PRBs or RBGs, of the common CORESET. The MIB caninclude SS block transmission mode, such as 1 bit. The MIB can include14 spare bits. The MIB can include CRC, such as 16 bits.

According to a possible embodiment for Random Access Channel (RACH)configuration, a UE can determine a RACH time and frequency resourcebased on combination of semi-static configuration signaling and dynamicindication signaling. Semi-static RACH time and frequency resources canbe cell-specifically configured, and a gNodeB can indicate the actualavailability of the semi-statically configured RACH resources viaDownlink Control Information (DCI) in a RACH slot or near the RACH slot,such as one or two slots before the RACH slot. The RACH slot can includeone or more semi-statically configured common, such as cell-specific,RACH resources. Considering that the number of available uplink symbolsin a slot may change in a slot basis, the UE may have to adjust apreamble format in each RACH slot.

According to a possible implementation, information for RACH resourcescan be indicated to UE via a semi-static configuration signaling. Forexample, the rate of occurrence of RACH slots and a starting RACH slotindex can be indicated. Alternatively, a set of RACH slots can beindicated. Also, the number of RACH occasions in the frequency domainper RACH slot (or at a given time instance) for a set of SS blocks, suchas equivalent to a set of gNodeB transmit beams, associated with thesame RACH time/frequency resource can be indicated. This may be relatedto the averaged and/or expected number of RACH attempts on the RACHresources associated with the set of SS blocks. Additionally, the numberof RACH occasion sets in the frequency domain per RACH slot (or at agiven time instance) can be indicated. Each RACH occasion set comprisingone or more RACH occasions can be associated with a set of SS blocks ora set of gNodeB transmit beams. This may be related to gNodeB antennaand/or beamforming architecture, such as a number of Radio Frequency(RF) chains. Furthermore, one or more RACH preamble formats can beindicated. Each preamble format can determine the number of RACHOFDM/SC-FDMA symbols per RACH preamble, the number of RACH preambles perRACH preamble format, a cyclic prefix (CP) length, and a guard timeduration. Since the number of available uplink symbols in a slot canvary dynamically, a couple of RACH preamble formats, each of which mayhave a different number of RACH preambles and/or a different number ofRACH OFDM/SC-FDMA symbols per RACH preamble, may need to besemi-statically configured.

Information for RACH resources can be indicated via dynamic signaling,such as DCI in group-common PDCCH. The group common PDCCH can be Txbeamformed with Tx beams that are associated with an addressed RACHresource. Equivalently, the group common PDCCH can be spatiallyquasi-co-located with a SS block and/or a CSI-RS resource which can beassociated with the addressed RACH resource. Then, UEs selecting theaddressed RACH resource based on downlink Tx beam selection(equivalently, SS block and/or CSI-RS resource selection) can receiveand decode the group common PDCCH and determine whether to transmit RACHpreamble(s) or not on the addressed RACH resource. Whether theconfigured potential RACH resource in a slot is available or not can beindicated via explicit or implicit indication. Starting and endinglocations, such as a starting symbol index and an ending symbol index,of RACH resources or uplink OFDM/SC-FDMA symbols within a slot can alsobe indicated. Alternatively, an indication of RACH preamble formatselected from the configured RACH preamble formats can be signaled.

According to a possible embodiment, the UE can be configured byhigher-layers, such as RRC semi-static signaling, with slots with RACHresources and periodicity, which can be in addition to other RACHconfiguration signaling. The UE can assume the RACH resources arepresent in the configured slot if the UE is not configured to monitor agroup common PDCCH in the slot or the UE may not decode a group commonPDCCH in the slot if configured to monitor a group common PDCCH. In oneexample, the UE may further identify a whole or a part ofsemi-statically configured RACH resources which can be assumed by the UEto be always available, based on information of semi-staticuplink/downlink configuration and/or actually transmitted SS blocks in acell. If the UE decodes the group common PDCCH in the slot, the groupcommon PDCCH can include an indication on whether the higher-layerconfigured RACH resource in the slot can be used for RACH transmissionand/or can signal a new RACH resource in the slot the UE can use fortransmission of RACH.

According to another possible embodiment for RACH configuration, acommon RACH resource configuration of a handover target cell indicatedin a handover command can be different from a common RACH resourceconfiguration advertised in a System Information Block (SIB) of thehandover target cell. A UE-specific RACH time/frequency resource forhandover can be selected from the common RACH resource configurationindicated in the handover command. Configuring additional RACH slots forhandover UEs can reduce the RACH related latency during handover, sincea higher number of configured RACH slots can potentially increaseactually available RACH resources. Thus, the common RACH resourceconfiguration indicated in the handover command can have more RACH slotsor more RACH time/frequency resources than the common RACH resourceconfiguration indicated in the SIB. This can accommodate fast handoverwithout impacting UEs in the target cell, since monitoring occasions forgroup common PDCCH for non-handover UEs in the target cell and thesystem information of the target cell may remain the same. According toa possible implementation, the common RACH resource configurationindicated in the handover command can include the common RACH resourceconfiguration advertised in the SIB and an additional common RACHresource configuration that provides additional RACH time/frequencyresources.

FIG. 6 is an example flowchart 600 illustrating the operation of awireless communication device, such as the UE 110, according to apossible embodiment. At 610, SS of a SS block of a SS burst set can bereceived. At 620, a measurement can be performed at least on thereceived SS of the SS block. For example, mobility measurement can beperformed that can include determining RSRP based on the received SS.

At 630, a PBCH of the SS block can be received. The PBCH can include afirst portion of the PBCH and a second portion of the PBCH. According toa possible implementation, the first portion of the PBCH can be anM-PBCH and the second portion of the PBCH can be a S-PBCH. The firstportion of the PBCH can be a first set of REs and the second portion ofthe PBCH can be a second set of REs. The first set of REs and the secondset of REs can be mutually exclusive. Alternately, the first set of REscan at least partially overlap with the second set of REs. The secondset of REs can include a part of PBCH OFDM symbols. The second set ofREs can also include a part of a PBCH frequency band.

The first portion of the PBCH can carry at least a part of minimumsystem information. Minimum system information can be information neededto access a cell. The minimum system information can be in a MIB. Thepart of minimum system information can include an indication of a partof SFN information.

The second portion of the PBCH can carry timing information. The timinginformation can be in a STIB that includes a SS block index. The timinginformation can include information including at least an indication ofa SS block index of the SS block within the SS burst set. The part ofminimum system information and the timing information can be separatelyencoded and modulated to separate sets of modulation symbols. The partof minimum system information and the timing information can also bejointly encoded. For example, the part of minimum system information andthe timing information can be jointly encoded into a common set ofmodulation symbols, such as occupying a common set of resource elements.

At 640, the second portion of the PBCH can be demodulated and decoded.The first portion of the PBCH can also be demodulated and decoded.Decoding the first portion of the PBCH can include cancelinginterference from the second portion of the PBCH. According to apossible implementation, the jointly encoded bits of the part of minimumsystem information can be encoded into a first self-decodable unit. Thejointly encoded bits of the timing information can be encoded intosecond self-decodable unit. The part of minimum system information canbe decoded from the first self-decodable unit. The timing informationcan be decoded from the second self-decodable unit.

At 650, the SS block index of the SS block within the SS burst set canbe determined at least based on the demodulating and decoding. At 660, ameasurement report can be transmitted. The measurement report caninclude a measurement quantity from the measurement on the received SSof the SS block and can include the determined SS block index.

FIG. 7 is an example flowchart 700 illustrating the operation of awireless communication device, such as the network entity 120, accordingto a possible embodiment. At 710, a SS of a SS block of a SS burst setcan be transmitted. For example, the SS of the SS block of the SS burstset can be configured and transmitted.

At 720, a PBCH of the SS block can be transmitted. For example, the PBCHcan be configured and transmitted. The PBCH can include a first portionof the PBCH and a second portion of the PBCH. The first portion of thePBCH can include a first set of REs and the second portion of the PBCHcan include a second set of REs. The second set of REs can include apart of PBCH OFDM symbols. The second set of REs can also include a partof a PBCH frequency band. The first set of REs and the second set of REscan be mutually exclusive. Alternately, the first set of REs can atleast partially overlap with the second set of REs. The first portion ofthe PBCH can cancel interference from the second portion of the PBCHwhen the first portion of the PBCH is decoded.

The first portion of the PBCH can carry at least a part of minimumsystem information. The part of minimum system information can includean indication of a part of SFN information. The second portion of thePBCH can carry timing information.

The timing information can include information including at least anindication of a SS block index of the SS block within the SS burst set.The part of minimum system information and the timing information can beseparately encoded and modulated to separate sets of modulation symbols.The part of minimum system information and the timing information canalso be jointly encoded. Jointly encoded bits of the part of minimumsystem information can be encoded into a first self-decodable unit.Jointly encoded bits of the timing information can be encoded intosecond self-decodable unit.

At 730, a measurement report can be received. The measurement report caninclude a measurement quantity from a measurement on the transmitted SSof the SS block. The measurement report can also include a SS blockindex of the SS block within the SS burst set.

FIG. 8 is an example flowchart 800 illustrating the operation of awireless communication device, such as the UE 110, according to apossible embodiment. At 810, an indication of a set of semi-staticallyconfigured RACH resources can be received via a higher layer signaling.The higher layer can be higher than a physical layer. For example, thehigher layer signaling can be RRC signaling. The set of semi-staticallyconfigured RACH resources can be common RACH resources. Common RACHresources can be cell-specific and can be common among multiple UEs.

The higher layer signaling can also include information of a set of RACHslots. The higher layer signaling can additionally include at least oneRACH preamble format. Each of the at least one RACH preamble format candefine at least a number of RACH symbols per RACH preamble and a numberof RACH preambles per RACH preamble format. The RACH symbols can be OFDMor SC-FDMA symbols.

At 820, an indication of availability of a RACH resource of at least oneRACH resource of the set of semi-statically configured RACH resourcescan be received via a dynamic physical-layer signaling. The dynamicphysical-layer signaling can be DCI in a group-common PDCCH. The groupcommon PDCCH can be spatially quasi-co-located with at least one of oneor more Synchronization Signal and PBCH blocks and one or more channelstate information-reference signal (CSI-RS) resources that areassociated with the RACH resource. The dynamic physical-layer signalingcan be within a number of slots including a RACH slot. The number ofslots can be two, can be one, or can be any other number of slotsincluding the RACH slot. For example, the number of slots can be two andthe RACH slot in the two slots can be slot n and the other slot in thetwo slots can be slot n−1. According to a possible embodiment, theindication of availability of the RACH can be received via a dynamicphysical-layer signaling in the RACH slot. The RACH slot can include theat least one RACH resource of the set of semi-statically configured RACHresources.

An indication of a number of frequency domain multiplexed RACH occasionscan be also received at a given time instance. Each RACH occasion can beassociated with at least one SS block. RACH resources can include time,frequency, and preambles of RACHs, whereas RACH occasions can includetime and frequency of RACHs. An indication of a number of time domainmultiplexed RACH occasions can additionally be received in the RACHslot.

An indication of a RACH preamble format selected from the at least oneRACH preamble format for the available RACH resource can also bereceived. The indication of a RACH preamble format can be received viathe dynamic physical-layer signaling.

Information of a number of uplink symbols in the RACH slot canadditionally be received. A RACH preamble format can be selected fromthe at least one RACH preamble format for the available RACH resourcebased on the received information of the number of uplink symbols in theRACH slot.

According to a possible implementation, the set of semi-staticallyconfigured RACH resources can be a first set of semi-staticallyconfigured RACH resources for a serving cell. An indication of a secondset of semi-statically configured RACH resources for a handover targetcell can be received. The indication of a second set of semi-staticallyconfigured RACH resources can be received in a handover command message.The second set of semi-statically configured RACH resources can bedifferent from a third set of semi-statically configured RACH resourcesfor at least one RACH resource. The third set of semi-staticallyconfigured RACH resources can be broadcast in a SIB of the handovertarget cell.

The second set of semi-statically configured RACH resources can includea first number of RACH slots and the third set of semi-staticallyconfigured RACH resources can include a second number of RACH slots,where the first number of RACH slots can be different from the secondnumber of RACH slots. For example, the first number of RACH slots can belarger than the second number of RACH slots.

The third set of semi-statically configured RACH resources can be asubset of the second set of semi-statically configured RACH resources.For example, the total resources in the third set of semi-staticallyconfigured RACH resources can be different from the total resources inthe second set of semi-statically configured RACH resources. Toelaborate, the second set of semi-statically configured RACH resourcescan include at least one RACH resource that is not in the third set ofsemi-statically configured RACH resources.

At 830, an available RACH resource in the RACH slot can be determinedbased on the received indication of the set of semi-staticallyconfigured RACH resources and based on the received indication ofavailability of the RACH resource of the at least one RACH resource ofthe set of semi-statically configured RACH resources.

At 840, a RACH preamble can be transmitted on the available RACHresource in the RACH slot. For example, available RACH resource can beassociated with a set of RACH preambles and the transmitted RACHpreamble can be from the set of RACH preambles. Transmitting can includetransmitting the RACH preamble on the available RACH resource in theRACH slot according to the indicated RACH preamble format.

Transmitting can also include transmitting the RACH preamble on theavailable RACH resource in the RACH slot according to the selected RACHpreamble format. For example, the information of a number of uplinksymbols in a RACH slot can be received in a physical layer signalingfrom a serving cell, and the RACH preamble format can be selected basedon the received information of the number of uplink symbols in the RACHslot.

FIG. 9 is an example flowchart 900 illustrating the operation of awireless communication device, such as the network entity 120, accordingto a possible embodiment. At 910, a set of RACH resources can bedetermined. At 920, the determined set of RACH resources can beconfigured semi-statically. The set of semi-statically configured RACHresources can be common RACH resources.

At 930, an indication of the set of semi-statically configured RACHresources can be transmitted via a higher layer signaling. The higherlayer can be higher than a physical layer. The higher layer signalingcan include information of a set of RACH slots. The higher layersignaling can also include at least one RACH preamble format. Each ofthe at least one RACH preamble format can define at least a number ofRACH symbols per RACH preamble and a number of RACH preambles per RACHpreamble format.

The set of semi-statically configured RACH resources can be a first setof semi-statically configured RACH resources for a serving cell. Anindication of a second set of semi-statically configured RACH resourcesfor a handover target cell can additionally be transmitted. Theindication of the second set of semi-statically configured RACHresources can be transmitted in a handover command message. The secondset of semi-statically configured RACH resources can be different from athird set of semi-statically configured RACH resources for at least oneRACH resource. The third set of semi-statically configured RACHresources can be broadcast in a system information block (SIB) of thehandover target cell.

The second set of semi-statically configured RACH resources can be afirst number of RACH slots and the third set of semi-staticallyconfigured RACH resources can be a second number of RACH slots. Thefirst number of RACH slots can be different from the second number ofRACH slots. The first number can be larger than the second number. Thethird set of semi-statically configured RACH resources can be a subsetof the second set of semi-statically configured RACH resources.

At 940, an indication of availability of a RACH resource of at least oneRACH resource of the set of semi-statically configured RACH resourcescan be transmitted via a dynamic physical-layer signaling. The dynamicphysical-layer signaling can be within a number of slots including aRACH slot. The dynamic physical-layer signaling can be DCI in agroup-common PDCCH. The group common PDCCH can be spatiallyquasi-co-located with at least one of one or more Synchronization Signaland PBCH blocks and one or more CSI-RS resources that are associatedwith the RACH resource. The RACH slot can include the at least one RACHresource of the set of semi-statically configured RACH resources.

An indication of a RACH preamble format selected from the at least oneRACH preamble format for the available RACH resource can additionally betransmitted. The indication of a RACH preamble format can be transmittedvia the dynamic physical-layer signaling.

An indication of a number of frequency domain multiplexed RACH occasionsat a given time instance can be also transmitted. Each RACH occasion canbe associated with at least one SS block. Also, an indication of anumber of time domain multiplexed RACH occasions in the RACH slot can betransmitted. Information of a number of uplink symbols in the RACH slotcan further be transmitted.

At 950, a RACH preamble can be received on the available RACH resourceof the set of semi-statically configured RACH resources in the RACHslot. The RACH preamble can be received on the available RACH resourcein the RACH slot according to the indicated RACH preamble format. TheRACH preamble can be received on the available RACH resource in the RACHslot according to a selected RACH preamble format from the at least oneRACH preamble format for the available RACH resource based on thetransmitted information of the number of uplink symbols in the RACHslot.

It should be understood that, notwithstanding the particular steps asshown in the figures, a variety of additional or different steps can beperformed depending upon the embodiment, and one or more of theparticular steps can be rearranged, repeated or eliminated entirelydepending upon the embodiment. Also, some of the steps performed can berepeated on an ongoing or continuous basis simultaneously while othersteps are performed. Furthermore, different steps can be performed bydifferent elements or in a single element of the disclosed embodiments.

FIG. 10 is an example block diagram of an apparatus 1000, such as the UE110, the network entity 120, or any other wireless communication devicedisclosed herein, according to a possible embodiment. The apparatus 1000can include a housing 1010, a controller 1020 coupled to the housing1010, audio input and output circuitry 1030 coupled to the controller1020, a display 1040 coupled to the controller 1020, a transceiver 1070coupled to the controller 1020, at least one antenna 1075 coupled to thetransceiver 1070, a user interface 1060 coupled to the controller 1020,a memory 1050 coupled to the controller 1020, and a network interface1080 coupled to the controller 1020. The apparatus 1000 may notnecessarily include all of the illustrated elements for differentembodiments of the present disclosure. The apparatus 1000 can performthe methods described in all the embodiments.

The display 1040 can be a viewfinder, a Liquid Crystal Display (LCD), aLight Emitting Diode (LED) display, an Organic Light Emitting Diode(OLED) display, a plasma display, a projection display, a touch screen,or any other device that displays information. The transceiver 1070 canbe one or more transceivers that can include a transmitter and/or areceiver. The audio input and output circuitry 1030 can include amicrophone, a speaker, a transducer, or any other audio input and outputcircuitry. The user interface 1060 can include a keypad, a keyboard,buttons, a touch pad, a joystick, a touch screen display, anotheradditional display, or any other device useful for providing aninterface between a user and an electronic device. The network interface1080 can be a Universal Serial Bus (USB) port, an Ethernet port, aninfrared transmitter/receiver, an IEEE 1394 port, a wirelesstransceiver, a WLAN transceiver, or any other interface that can connectan apparatus to a network, device, and/or computer and that can transmitand receive data communication signals. The memory 1050 can include aRandom Access Memory (RAM), a Read Only Memory (RON), an optical memory,a solid state memory, a flash memory, a removable memory, a hard drive,a cache, or any other memory that can be coupled to an apparatus.

The apparatus 1000 or the controller 1020 may implement any operatingsystem, such as Microsoft Windows®, UNIX®, or LINUX®, Android™, or anyother operating system. Apparatus operation software may be written inany programming language, such as C, C++, Java or Visual Basic, forexample. Apparatus software may also run on an application framework,such as, for example, a Java® framework, a .NET® framework, or any otherapplication framework. The software and/or the operating system may bestored in the memory 1050 or elsewhere on the apparatus 1000. Theapparatus 1000 or the controller 1020 may also use hardware to implementdisclosed operations. For example, the controller 1020 may be anyprogrammable processor. Disclosed embodiments may also be implemented ona general-purpose or a special purpose computer, a programmedmicroprocessor or microprocessor, peripheral integrated circuitelements, an application-specific integrated circuit or other integratedcircuits, hardware/electronic logic circuits, such as a discrete elementcircuit, a programmable logic device, such as a programmable logicarray, field programmable gate-array, or the like. In general, thecontroller 1020 may be any controller or processor device or devicescapable of operating an apparatus and implementing the disclosedembodiments. Some or all of the additional elements of the apparatus1000 can also perform some or all of the operations of the disclosedembodiments.

According to a possible embodiment as a UE, the transceiver 1070 canreceive a SS of a SS block of a SS burst set. The controller 1020 canperform a measurement at least on the received SS of the SS block.

The transceiver 1070 can receive a PBCH of the SS block. The PBCH caninclude a first portion of the PBCH and a second portion of the PBCH.The first portion of the PBCH can carry at least a part of minimumsystem information. The part of minimum system information can includean indication of a part of SFN information. The second portion of thePBCH can carry timing information. The timing information can includeinformation including at least an indication of a SS block index of theSS block within the SS burst set. The first portion of the PBCH caninclude a first set of resource elements REs and the second portion ofthe PBCH can include a second set of REs. The first set of REs and thesecond set of REs can be mutually exclusive. Alternately, the first setof REs can at least partially overlap with the second set of REs. Thecontroller 1020 can demodulate and decode the first portion of the PBCH.Decoding the first portion of the PBCH can include cancelinginterference from the second portion of the PBCH.

The part of minimum system information and the timing information can beseparately encoded and modulated to separate sets of modulation symbols.The part of minimum system information and the timing information canalso be jointly encoded. For example, jointly encoded bits of the partof minimum system information can be encoded into a first self-decodableunit. Jointly encoded bits of the timing information can be encoded intosecond self-decodable unit.

The controller 1020 can demodulate and decode the second portion of thePBCH. The controller 1020 can decode the part of minimum systeminformation from the first self-decodable unit. The controller 1020 candecode the timing information from the second self-decodable unit.

The controller 1020 can determine the SS block index of the SS blockwithin the SS burst set at least based on the demodulating and decoding.The transceiver 1070 can transmit a measurement report. The measurementreport can include a measurement quantity from the measurement on thereceived SS of the SS block and includes the determined SS block index.

According to a possible embodiment as a network entity, the controller1020 can configure a SS of a SS block of a SS burst set. The transceiver1070 can transmit the SS of the SS block of the SS burst set. Thetransceiver 1070 can transmit a PBCH of the SS block. The PBCH caninclude a first portion of the PBCH and a second portion of the PBCH.The first portion of the PBCH can carry at least a part of minimumsystem information. The second portion of the PBCH can carry timinginformation. The timing information can include information including atleast an indication of a SS block index of the SS block within the SSburst set. The transceiver 1070 can receive a measurement report. Themeasurement report can include a measurement quantity from a measurementon the transmitted SS of the SS block and can include a SS block indexof the SS block within the SS burst set.

According to a possible embodiment as a UE, the transceiver 1070 canreceive an indication of a set of semi-statically configured RACHresources via a higher layer signaling, where the higher layer is higherthan a physical layer. The higher layer signaling can include at leastone RACH preamble format. Each of the at least one RACH preamble formatcan define at least a number of RACH symbols per RACH preamble and anumber of RACH preambles per RACH preamble format.

The transceiver 1070 can also receive an indication of availability of aRACH resource of at least one RACH resource of the set ofsemi-statically configured RACH resources via a dynamic physical-layersignaling. The dynamic physical-layer signaling can be within a numberof slots including a RACH slot. The RACH slot can include the at leastone RACH resource of the set of semi-statically configured RACHresources.

The transceiver 1070 can additionally receive an indication of a numberof frequency domain multiplexed RACH occasions at a given time instance.Each RACH occasion can be associated with at least one SS block. Thetransceiver 1070 can further receive an indication of a RACH preambleformat selected from the at least one RACH preamble format for theavailable RACH resource. The indication of a RACH preamble format can bereceived via the dynamic physical-layer signaling.

The transceiver 1070 can also receive information of a number of uplinksymbols in the RACH slot. The controller 1020 can select a RACH preambleformat from the at least one RACH preamble format for the available RACHresource based on the received information of the number of uplinksymbols in the RACH slot.

The controller 1020 can determine an available RACH resource in the RACHslot based on the received indication of the set of semi-staticallyconfigured RACH resources and based on the received indication ofavailability of the RACH resource of the at least one RACH resource ofthe set of semi-statically configured RACH resources.

The transceiver 1070 can transmit a RACH preamble on the available RACHresource in the RACH slot. Transmitting can include transmitting theRACH preamble on the available RACH resource in the RACH slot accordingto the indicated RACH preamble format. Transmitting can also includetransmitting the RACH preamble on the available RACH resource in theRACH slot according to the selected RACH preamble format.

According to a possible implementation, the set of semi-staticallyconfigured RACH resources can be a first set of semi-staticallyconfigured RACH resources for a serving cell. The transceiver 1070 canreceive an indication of a second set of semi-statically configured RACHresources for a handover target cell. The indication of the second setof semi-statically configured RACH resources is received in a handovercommand message. The second set of semi-statically configured RACHresources can be different from a third set of semi-staticallyconfigured RACH resources for at least one RACH resource. The third setof semi-statically configured RACH resources can be broadcast in asystem information block (SIB) of the handover target cell.

According to another possible embodiment as a network entity, thecontroller 1020 can determine a set of random access channel resourcesand configure, semi-statically, the determined set of random accesschannel resources. The transceiver 1070 can transmit an indication ofthe set of semi-statically configured RACH resources via a higher layersignaling. The higher layer can be higher than a physical layer. Thetransceiver 1070 can transmit an indication of availability of a RACHresource of at least one RACH resource of the set of semi-staticallyconfigured RACH resources via a dynamic physical-layer signaling. Thedynamic physical-layer signaling can be within a number of slotsincluding a RACH slot. The RACH slot can include the at least one RACHresource of the set of semi-statically configured RACH resources. Thetransceiver 1070 can receive a RACH preamble on the available RACHresource of the set of semi-statically configured RACH resources in theRACH slot.

The method of this disclosure can be implemented on a programmedprocessor. However, the controllers, flowcharts, and modules may also beimplemented on a general purpose or special purpose computer, aprogrammed microprocessor or microcontroller and peripheral integratedcircuit elements, an integrated circuit, a hardware electronic or logiccircuit such as a discrete element circuit, a programmable logic device,or the like. In general, any device on which resides a finite statemachine capable of implementing the flowcharts shown in the figures maybe used to implement the processor functions of this disclosure.

While this disclosure has been described with specific embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. For example,various components of the embodiments may be interchanged, added, orsubstituted in the other embodiments. Also, all of the elements of eachfigure are not necessary for operation of the disclosed embodiments. Forexample, one of ordinary skill in the art of the disclosed embodimentswould be enabled to make and use the teachings of the disclosure bysimply employing the elements of the independent claims. Accordingly,embodiments of the disclosure as set forth herein are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure.

In this document, relational terms such as “first,” “second,” and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The phrase“at least one of,” “at least one selected from the group of,” or “atleast one selected from” followed by a list is defined to mean one,some, or all, but not necessarily all of, the elements in the list. Theterms “comprises,” “comprising,” “including,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element proceeded by “a,” “an,” or the like does not,without more constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element. Also, the term “another” is defined as at least a second ormore. The terms “including,” “having,” and the like, as used herein, aredefined as “comprising.” Furthermore, the background section is writtenas the inventor's own understanding of the context of some embodimentsat the time of filing and includes the inventor's own recognition of anyproblems with existing technologies and/or problems experienced in theinventor's own work.

We claim:
 1. A method in a user equipment, the method comprising:receiving a first configuration of a first set of random access channeloccasions, where the first configuration of the first set of randomaccess channel occasions is received in a handover command message froma first cell; receiving a second configuration of a second set of randomaccess channel occasions of a second cell, wherein the second set ofrandom access channel occasions is different from the first set ofrandom access channel occasions, and wherein system information of thesecond cell includes the second configuration of the second set ofrandom access channel occasions; and transmitting a random accesschannel preamble on a random access channel occasion, where at least oneselected from the first set of random access channel occasions and thesecond set of random access channel occasions includes the random accesschannel occasion, wherein the first cell is different from the secondcell.
 2. The method according to claim 1, wherein the first cell is aserving cell and the second cell is a handover target cell.
 3. Themethod according to claim 1, wherein the random access channel occasionis an available random access channel occasion of the second set ofrandom access channel occasions, and wherein the method furthercomprises: receiving an indication of availability of the availablerandom access channel occasion of the second set of random accesschannel occasions via a dynamic physical-layer signaling, where thedynamic physical-layer signaling is within a number of slots including arandom access channel slot, wherein the random access channel slotincludes at least one random access channel occasion of the second setof random access channel occasions including the random access channeloccasion; and determining the available random access channel occasionin the random access channel slot based on the second configuration ofthe second set of random access channel occasions and based on theindication of availability of the available random access channeloccasion of the second set of random access channel occasions.
 4. Themethod according to claim 3, wherein the dynamic physical-layersignaling is downlink control information in a group-common physicaldownlink control channel.
 5. The method according to claim 4, whereinthe group common physical downlink control channel is spatiallyquasi-co-located with at least one of one or more synchronization signaland physical broadcast channel blocks and one or more channel stateinformation-reference signal occasions that are associated with therandom access channel occasion.
 6. The method according to claim 1,wherein the first configuration of the first set of random accesschannel occasions includes information of a set of random access channelslots, where a random access channel slot of the set of random accesschannel slots includes at least one random access channel occasion ofthe first set of random access channel occasions.
 7. The methodaccording to claim 6, wherein the first configuration of the first setof random access channel occasions further includes an indication of anumber of time domain multiplexed random access channel occasions ineach random access channel slot of the set of random access channelslots.
 8. The method according to claim 1, wherein the firstconfiguration of the first set of random access channel occasionsincludes an indication of a number of frequency domain multiplexedrandom access channel occasions at a given time instance, where eachrandom access channel occasion is associated with at least onesynchronization signal and physical broadcast channel block.
 9. Themethod according to claim 1, wherein the first configuration of thefirst set of random access channel occasions includes information of arandom access channel preamble format, wherein the random access channeloccasion is from the first set of random access channel occasions, andwherein a duration of the random access channel preamble is determinedbased on the random access channel preamble format.
 10. The methodaccording to claim 1, wherein the second configuration of the second setof random access channel occasions includes a configuration of at leastone random access channel preamble format, wherein the method furthercomprises receiving information of a random access channel preambleformat selected from the at least one random access channel preambleformat, where the information of a random access channel preamble formatis received via a dynamic physical-layer signaling, and whereintransmitting comprises transmitting the random access channel preambleon the random access channel occasion according to the received randomaccess channel preamble format.
 11. The method according to claim 10,further comprising: receiving information of a number of uplink symbolsin a random access channel slot, where the random access channel slotincludes at least the random access channel occasion; and selecting arandom access channel preamble format from the at least one randomaccess channel preamble format for the random access channel occasionbased on the received information of the number of uplink symbols in therandom access channel slot, wherein transmitting comprises transmittingthe random access channel preamble on the random access channel occasionin the random access channel slot according to the selected randomaccess channel preamble format.
 12. The method according to claim 1,wherein the first set of random access channel occasions is a subset ofthe second set of random access channel occasions.
 13. The methodaccording to claim 1, wherein the second set of random access channeloccasions is a subset of the first set of random access channeloccasions.
 14. The method according to claim 1, wherein the first set ofrandom access channel occasions comprises a first number of randomaccess channel slots and the second set of random access channeloccasions comprises a second number of random access channel slots,where the first number of random access channel slots is different fromthe second number of random access channel slots.
 15. The methodaccording to claim 14, wherein the first number is larger than thesecond number.
 16. An apparatus comprising: a controller that controlsoperations of the apparatus; and a transceiver coupled to thecontroller, where the transceiver receives a first configuration of afirst set of random access channel occasions, where the firstconfiguration of the first set of random access channel occasions isreceived in a handover command message from a first cell, receives asecond configuration of a second set of random access channel occasionsof a second cell, wherein the second set of random access channeloccasions is different from the first set of random access channeloccasions, and wherein system information of the second cell includesthe second configuration of the second set of random access channeloccasions, and transmits a random access channel preamble on a randomaccess channel occasion, where at least one selected from the first setof random access channel occasions and the second set of random accesschannel occasions includes the random access channel occasion, whereinthe first cell is different from the second cell.
 17. The apparatusaccording to claim 16, wherein the first cell is a serving cell and thesecond cell is a handover target cell.
 18. The apparatus according toclaim 16, wherein the random access channel occasion is an availablerandom access channel occasion of the second set of random accesschannel occasions, and wherein the transceiver receives an indication ofavailability of the available random access channel occasion of thesecond set of random access channel occasions via a dynamicphysical-layer signaling, where the dynamic physical-layer signaling iswithin a number of slots including a random access channel slot, wherethe random access channel slot includes at least one random accesschannel occasion of the second set of random access channel occasionsincluding the random access channel occasion, and determines theavailable random access channel occasion in the random access channelslot based on the second configuration of the second set of randomaccess channel occasions and based on the indication of availability ofthe available random access channel occasion of the second set of randomaccess channel occasions.
 19. The apparatus according to claim 16,wherein the first configuration of the first set of random accesschannel occasions includes information of a set of random access channelslots, where a random access channel slot of the set of random accesschannel slots includes at least one random access channel occasion ofthe first set of random access channel occasions.
 20. The apparatusaccording to claim 16, wherein the first configuration of the first setof random access channel occasions includes an indication of a number offrequency domain multiplexed random access channel occasions at a giventime instance, where each random access channel occasion is associatedwith at least one synchronization signal and physical broadcast channelblock.